An important factor for the adequate operation of most refrigerating compressors is the adequate lubrication of the components thereof which have a relative movement between each other. The lubrication is obtained by pumping lubricant oil provided in an oil reservoir defined in the interior of a generally hermetic shell of said compressors, in a lower portion of said shell. This oil is pumped until reaching the parts with relative movement of the compressor, wherefrom said oil returns, for example, by gravity, to the oil reservoir.
In some known constructions, the compressor comprises a generally vertical crankshaft that carries a lubricant oil pump, which conducts said oil to the compressor parts to be lubricated, using the rotation of said crankshaft. In these constructions, the oil is pumped from the oil reservoir by spinning and mechanical dragging.
In this constructions, the crankshaft presents a portion of its extension provided, externally (WO2005/047699) or internally (WO96/29516), with helical grooves which conduct the lubricant oil from the oil reservoir to the relatively moving parts of the compressor distant from the oil reservoir.
In the solution WO2005/047699, a tubular sleeve is provided around part of the crankshaft which presents the helical grooves, said tubular sleeve being attached to the compressor shell or to the stator.
The solution WO96/29516 presents the crankshaft having part of its extension defining a conduct inside which is mounted, with a radial gap, a pump body, said solution presenting one of the parts of inner wall of the tubular shaft and outer wall of the pump body provided with helical grooves.
There are known some prior art solutions for oil pumping in variable speed compressors. In these constructions (WO93/22557, U.S. Pat. No. 6,450,785), the crankshaft inferiorly carries a pump body provided with surface channels and which is internally disposed in a tubular sleeve, one of the parts of pump body and tubular sleeve being rotatively stationary in relation to the other part, so as to allow a dragging effect on the oil being pumped by centrifugal force, resulting from the rotation of the motor.
Solution WO93/22557 presents the pump body, which is externally provided with helical grooves, affixed to the crankshaft, in order to rotate therewith, the tubular sleeve being attached to the electric motor, by a fixation rod, said tubular sleeve being mounted around the pump body with a radial gap.
This solution allows friction wear to occur between the parts of pump body and tubular sleeve, as well as mechanical losses, as a result of the rigid fixation between said tubular sleeve and the stator and of practically inevitable misalignments between the pump body and the tubular sleeve.
Solution U.S. Pat. No. 6,450,785 presents the pump body externally provided with helical grooves on its outer surface and inferiorly attached to the electric motor stator through a fixation rod with a “U”-shaped profile, and the tubular sleeve affixed to the crankshaft of the compressor, so as to rotate therewith. This solution presents a construction in which the fixation rod allows only a certain angular movement of the pump body around axes contained in the lower fixation plane of the pump body to the fixation rod, said plane being orthogonal to the crankshaft of the compressor. Thus, the fixation rod can be elastically deformed to permit the pump body to incline to accommodate itself in the interior of the tubular sleeve. However, as the pump body is not free to be displaced, in its entirety, in directions orthogonal to the crankshaft, it is not able to compensate for construction or mounting misalignments, so as to occupy a position in which its axis is concentric or parallel to the axis of the tubular sleeve.
Although reducing the friction wear and losses, this known prior art solution U.S. Pat. No. 6,450,785 also conducts to a certain efficiency loss, particularly considering the inevitable dimensional deviations of manufacture and mounting.